1. Field of the Invention
The present invention relates to a reflector, a light, a light-guiding plate, and a display.
2. Description of the Related Art
In a display of a PC, a liquid crystal television, etc., a side light type light is used. In the case of a transmission type liquid crystal display device, a planar lighting device (backlight) is arranged on the back surface side of the liquid crystal panel. A side light type backlight includes a light-guiding plate, a light source arranged on one side of the light-guiding plate, and a reflector.
A reflector has for example a semicircular sectional shape or U-shape and is arranged to cover the light source, extend to the end parts of the light-guiding plate, and partially overlap the light-guiding plate. The light striking the incident surface of the light-guiding plate proceeds inside the light-guiding plate while being reflected. Therefore, to make the light be emitted from the emission surface of the light-guiding plate, the light-guiding plate is formed into a wedge sectional shape or an optical element comprised of a prism array, microlens array, etc. is arranged there.
Light striking the light-guiding plate by a large angle is emitted from a position of the emission surface of the light-guiding plate near the light source and sometimes becomes a cause of bright lines at the emission surface. Further, the weak intensity light sometimes becomes a cause of dark lines at the emission surface. In a side light type backlight, there is the problem of the occurrence of uneven brightness including bright lines and dark lines.
Further, in a conventional side light type backlight, the entering surface is not processed at all, so there is the problem of the luminance near the light source ending up falling. FIG. 30 shows the results of verification of the luminance distribution in a perpendicular direction from the light source due to differences in treatment of entering surfaces. The reflection surface of the light-guiding plate uses a prism light-guiding plate and emits light from the emission surface inclined from the normal by 60 to 70 degrees. The emitted light is bent in the normal direction by the downward-facing prism lens sheet. From the results, it can be confirmed that the conventional luminance distribution in the flat state of the entering surface with no treatment given exhibits a drop in the luminance near about 20 mm near the light source.
To solve this problem, it has been proposed to roughen the incident surface of the light-guiding plate to eliminate the uneven luminance (see for example Patent Document 1 below). The light strikes the roughened incident surface and is scattered. The amount of light emitted from the part of the emission surface of the light-guiding plate near the light source increases, but the amount of light emitted from the part of the emission surface of the light-guiding plate far from the light source ends up becoming smaller. Further, part of the light scattered at the incident surface of the light-guiding plate is not effectively propagated inside the light-guiding plate and the efficiency of utilization of the light drops. The roughening is performed uniformly over the entire incident surface of the light-guiding plate.
FIG. 30 shows the luminance distributions in the case of attaching diffusion treated tapes instead of diffusion treatment of the entering surface. By diffusion treatment of the entering surface, the luminance near the light source rises, but the amount of light at the far part becomes smaller, so there was the problem that the luminance ended up gradually falling.
Further, there is a proposal to arrange a prism sheet between the light source and the light-guiding plate (for example, see Patent Documents 2 and 3 below). The diffusion light emitted from the light source is condensed by the prism sheet to become highly oriented light which strikes the incident surface of the light-guiding plate. However, if highly oriented light strikes the incident surface of the light-guiding plate, the amount of emission of light from the end part of the light-guiding plate near the light source becomes smaller and the uneven luminance at the end part of the light-guiding plate near the light source is not eliminated.
Further, there is a proposal to form grooves extending perpendicular to the emission surface of the light-guiding plate at the incident surface of the light-guiding plate (for example, see Patent Document 4 below). This prior art has as its object the provision of a display becoming darker at the end part positioned at the electrode of the lamp forming the light source.
Further, there is a proposal to form an inclined surface reflecting light at an end part of a reflection sheet arranged at a reflection surface side of a light-guiding plate at the side opposite to the emission surface (for example, see Patent Document 5 below). In this prior art, the phenomenon of wide angle light emitted from the light source being reflected at the end part of the reflection sheet and striking the light-guiding plate is prevented by making such light be reflected at the inclined surface of the reflection sheet and returning it to the light source side. Due to this, the appearance of bright lines at the emission surface of the light-guiding plate is prevented. However, this prior art can only be used in a basic configuration where the end part of the reflection sheet is arranged between the light-guiding plate and one end part of the reflector, and the other end part of the reflector is in close contact with the light-guiding plate. When the end part of the reflection sheet is arranged at the outside from one end part of the reflector or when there is a gap between the other end part of the reflector and the light-guiding plate, this prior art cannot be applied.
Patent Document 1: Japanese Unexamined Patent Publication (A) No. 9-160035
Patent Document 2: Japanese Unexamined Patent Publication (A) No. 9-166713
Patent Document 3: Japanese Unexamined Patent Publication (A) No. 2000-260216
Patent Document 4: Japanese Unexamined Patent Publication (A) No. 10-253957
Patent Document 5: Japanese Unexamined Patent Publication (A) No. 2002-216522